A parallel-plate capacitor with plate area \(A\) is charged to a net free charge \(+Q\) on its top plate and \(-Q\) on its bottom plate, then disconnected from the voltage source. The space between the plates is filled by two uniform dielectric slabs stacked on top of one another. Slab 1 (dielectric constant \(\kappa_1\)) rests against the top plate, and Slab 2 (dielectric constant \(\kappa_2\)) rests against the bottom plate, meeting Slab 1 at a planar interface parallel to the plates. Which of the following gives the correct ratio of the electric field magnitudes \(E_1 / E_2\) inside the two slabs, and the net bound surface charge density \(\sigma_b\) accumulated at the interface between Slab 1 and Slab 2?